ENV334H1 Lecture 13: L13-Restoration

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Restoration Ecology: Ecosystem restoration, rehabilitation & reclamation
March 13, 2017
Restoration Ecology
• Bradshaw said this in the 80s:
o Well and fine to try and understand communities, and ecosystems
o But acid test for checking that we’re understanding any kind of process, is not that we can
take ecosystems to bits of pieces of paper, but can we actually put a community together
o Experiments of what can we achieve with all of the knowledge we’ve got
• Ecological restoration
o Movement that started in early 2000s
o Process of assisting the recovery of an ecosystem that has been degraded, damaged, or
destroyed
o A lot of material we can work with, but seldom have data
Probability of Rapid and Full Ecological Restoration
• Original ecosystem (green star)
• Can think of disturbances both in terms of scale (how much of landscape was disturbed), and
degree/intensity of disturbance
• Small-scale disturbance that’s not to intense, then recovery rapid
o Community will probably come back to what it was before
o Size of circle = probability that system comes back
• Fairly small-scale (spatial scale) but very intense = more difficult to come back to original state
• Low intensity disturbance, but spans large proportion of landscape, then harder to come back from
• If have large and severe disturbance, then system is unlikely to come back to original state
o Or might take long time to recover
Ecological Restoration
• 3 different categories:
[1] Restoration
• Attempt to return ecosystem to historic condition
• Recreate it in terms of species and function
[2] Rehabilitation
• Had change, but now conditions aren’t same as before
• Can’t restore all of it to what it was before
• Try to recreate some ecosystem processes (some of the function) but not aiming to make sure all the
species are there
• = Functional restoration
• Won’t see same species
• 1 step below full restoration
[3] Reclamation
• Such a degraded system that there’s no hope of even getting function back
• Just want an ecosystem
• Maybe just have a cover so soils don’t erode away
• Might have to recreate a whole new ecosystem
• 3 levels of restoration that mean you’re going back (or not) to some state Diagnose Damage
• Start with fully functionally intact system
• Then some kind of stress or disturbance
o Community changed to sthg really different maybe that wasn’t functional
o Along the way might have lost a lot of species
• Biotic threshold: Which species are there? How has it changed
• Abiotic threshold: Maybe physical chemical characteristics of site have actually changed
o Left with very degraded community
• Is it possible to get from state 6 back to state 1?
[1] Rehabilitation:
o Take state 6, and try to raise abiotic threshold or site so that can get some things back
o Get some abiotic conditions so that some organisms can live there that can re-establish some
sort of function
o But can’t go back to all the characteristics (all the species) or original conditions
▪ i.e. can’t get back to state 1
[2] Restoration
o Trying to get back all of your species
[3] Reclamation
o Very degraded
o Try to establish some organisms/function but nowhere close to original
Need Clear Goals
• If no goals, then won’t know where you’re going
• What you should measure to try to convince people that you achieved something
• Involving people to decide
• Restoring to what state?
o How far back in past do we want to restore this community to?
▪ Communities aren’t static
▪ Environmental conditions have changed over thousands and thousands of years
o Is that state we want still viable?
▪ Might have had changes (climate change, hydrology because of diff constructions)
▪ Might not have abiotic conditions to have those organisms
▪ Need to figure out what we can actually restore to
• Restoring what?
o Species
▪ Most projects want to restore all species that were there (biodiversity)
o Ecosystem functions
▪ Select certain ones
o Ecosystem services
▪ In general though, services come from function
▪ Just that the public doesn’t know what function is
Ecosystem Services
• 4 different services
• More for communication with public
• EAsier for government to communicate with public if speak in terms of services rather than ‘function’
[1] Supporting
• Primary production
o Food for food web
o Nutrient cycling [2] Provisioning
• What can we harvest and get out of ecosystems
• Fish, timber, fodder
[3] Regulating
• Ecosystem process that makes ecosystem
• EX: Herbivores/predators/biotic interactions, C sequestration, water supply (quality and quantity of
water), soil characteristics, pollination
[4] Cultural
• Esthetic values
Why is Biological Diversity Important?
• Implicit relationship between diversity of community and its function in ecosystem (how it makes
ecosystem function)
• Asking why we care about biodiversity (why does it matter if there’s 100 or 50 spp)
• General idea that ↑ diversity = ↑ function
• But probably not a straight line
o More of a plateauing line
o If increase biodiversity, will get more function (primary production, nutrient cycling)
o But eventually don’t get more function even if increase biodiversity
• If interested in effect of reducing biological diversity, how will this affect ecosystems?
o Species could be redundant
• 3 different hypotheses that are closely related
[1] Redundancy hypothesis
• People think that it means we can lose some species and it’s okay
• If went down in terms of biological species, tell us what number we should have to cover all the
functions
• But probably not the same species that will do that function
• Some species better under certain conditions
• EX: Have a few species doing N fixation (all same function)
o But some might do better in dry years and some better in wet years
o So still need all the species to provide insurance hypothesis
[2] Insurance hypothesis
• Species are redundant but don’t perform in same way
[3] Rivet hypothesis
• Species like rivets on plane
• Thousands of rivets on plane
• All hold plane together
• If lost one rivet on airplane is okay
• If 12 might still be okay
• But might lose so many that plane crashes and won’t be able to fly
• As losing diversity, maybe is somewhere where you fall off
• 3 hypotheses that are all linked together
• Function increases in non-linear way with biological diversity
• But we also think that curve isn’t a straight line
• Depends on which species we lose first
• If lose species, might be okay for a little, but eventually, function will decline
• Depending on which species lose first (maybe was keystone) could lose function quickly
• = Bottom boundary of blue area • Or maybe no keystone species, and only when you lose that particular species, system falls apart (top
boundary)
• Many possible routes
• Relationship between having species
• If can recover species, will recover ecosystem function
How to Restore
• Different steps to be taken
[1] Impact
• What was the impact on that particular area?
• Maybe was some change in community composition or architecture
[2] General Cause
[3] Intervention
• Differential site availability
o If there isn’t as much site available as before, then need to fix site:
o Remove disturbance
o Fix site
• Differential species availability
o Assisted dispersal
• Differential species performance
o Species aren’t performing properly
o Need to adjust either physical/chemical conditions of site
o i.e. maybe pH too high or too low
o Invasive species
• Causes determine interventions
General Restoration Principles
• Give general guidelines, but once you have specific project, need to adapt
• All of the points go from restoring locally, to restoring to larger and larger scales
• Trying to make large area self-sustaining
• First steps would be to restore environment to restore population itself:
o Want self-reproducing populations
o Not only is environment there but can reproduce and maintain itself
• Need to reduce threats
o EX: Reduce air pollution
• Then use assemblages of species characteristic to reference ecosystem that provide structure
o Should use native species when possible
o Sometimes native species not used:
▪ If losing soils quickly and natives grow slowly
▪ Natives might not establish fast enough
▪ Just need non-natives to stabilize soil
o Try to include all functional groups
▪ Idea of redundancy
▪ Have choice of different species we can have
▪ Want to restore ecosystem functions to what was there before
• Eventually have self-sustaining ecosystem
o As something that is self-functioning and that can resist/be resilient to periodic stress (dry/wet
year)
o Eventually work at landscape scale ▪ i.e. If have self-sustaining ecosystem, now want to try to reconnect to whole
landscape
o Try to work in larger and larger scale and try to get back to what was there before
Setting SMART Goals
• Need clear goals that you can monitor so that you know you were successful
• Specific
• Measure
• Achievable
• Reasonable
o Given funding, time, resources
• Time-bound
o Over specific time-bound
• If have all of this, then can follow what happens after you’ve done restoration
• Show that what you did has an effect
Monitoring and Evaluating Recovery
• Might have degraded site for which we have no previous data on
• Need to find reference site
o Site that is as similar as possible but hasn’t received particular disturbance
▪ EX: Around Sudbury area, have a lot of acid rain and have a lot of degraded state
▪ Won’t find reference site that’s right in Sudbury
▪ Need lakes of similar geography, similar rock composition
o Could also have more than 1 reference site
o Gather information on degraded site + reference sites
• Plan ACTION sometime down the line
o Maybe for a while not doing restoration, but just monitoring
o Where is that degraded site now compared to reference site
o Then plan action for that time
o How does that action affect degraded site?
o If had done no action, might have gone some way
o But hopefully, management will bring you back closer to reference site
o If have different ways to restore, might have to plan restoration around different options
o Some areas where have no actions
• Why is the No Action and reference site important?
o Say you have no reference site, and no action and management brings you up and you say
“Oh Yay”
o Why might that be not convincing?
▪ Increase in performance may be by chance
▪ Maybe was a good year by chance
o No reference site/action site, don’t know
Monitoring and Evaluating Recovery
• Mana Island NZ: Suite of islands
• Invaded late by Mauri’s (indigenous people) and then later by Europeans
• Europeans started cutting trees for agriculture
o Also brought in mammals
• NZ was separated from Australia before mammals evolved
• But Mauri’s and Europeans brought mammals • Ended up with a lot of big impacts from having mammals around
• A lot of original diversity of islands linked to bird diversity
o Many ground-nesting birds because no predators
o But mammals changed community
• Because the islands are small and isolated, was pretty easy to control the mammal populations
o On Mana island, eradicated all the mice
o If go to visit these islands, officials make sure you don’t have any animals
• Then planned experiments:
o Adaptive Management
▪ Had reference site
• = original forest
▪ Had areas that were disturbed that they wanted to restore by planting native plants
▪ Some places where didn’t take any action
• Kept some areas where didn’t do anything (no action) then other areas where
they did monitor
o Compare areas of no action to plantings
▪ Are we getting anywhere close to reference site?
Example 2: Restoration of Tallgrass Prairies
• When got to prairies, was grass there already, very productive, really flat
• So all of Midwest was turned into agriculture by Europeans
• Turned into fields, less than 1% of original prairies left
• In 1960s, people wanted to bring back tall-grass prairies with bison
• But very little of this environment left for the bison
• Neal Smith
o Put resources to coordinate projects and build up large projects
o Neal Smith Wildlife Refuge
o Goal of refuge is to restore original tall-grass prairies that were in this area
o Try to re-establish function and ecosystems
• Problem:
o Site has been farmed with fertilizer for long time
o Soils too productive for native species
▪ Need soils to be less productive
o Also no seeds available
o = Small remnant areas, but need to gather seeds, grow them again, to amplify seed bank to
start planting over large areas
Restoration of Tallgrass Prairies
• Try to get ecosystem back to what it was
• Try to take several things you can measure
• Prairies have a lot of organic carbon because roots or plants grow deep
• At beginning of project
• In remnant part of prairies, have some data
o Can be used to set target
• Should have ~50 mg/ha of OM
• If get trend, can predict how many years before we reach target in terms of soil organic carbon
o Useful to have target and then monitor after restoration to see if you’re approaching your
target March 16, 2017
Restoration of Tallgrass Prairies
• Trying to restore tallgrass ecosystems that were taken over when people moved west
• Try to restore them to vegetation that was there before
• Problems: soil too productive + loss of seeds
• Restored as best they could
o Tried to restore soil organic carbon
o Higher in prairie than in agricultural field
• Know that tallgrass prairie has organic carbon
• As monitor how things change through time
• Can get better timeline of whether it’s an achievable goal
• Organic content of soil was going up
Restoration of Tallgrass Prairies
• Then can start reintroducing animals
o Butterflies
o Bison
• Other targets:
o Soil organic carbon
o Sample soil in many different parts of reserve
o Streams also important
▪ Streams integrate themselves across landscape
▪ Monitored nitrate in streams
▪ Under agricultural had high concentrations because of fertilizers
▪ Konza prairie (areas that are more native) have lower concentration
• = get target from less-impacted area (reference)
Responses to Restoration
• 3 different models
• Is that system coming back to original state?
[1] Rubber band model
[2] Hysteresis model (Alternative Stable States)
[3] Humpty Dumpty model
[1] Rubber Band model
• Start with original ecosystem
• Add some degree of stress
o For a while system is okay
o Eventually if enough stress, system gets degraded
• In case of rubber band model:
o If you pull it then release it, will come back
o i.e. just remove stressor and system will come back
• Most likely to occur when:
o Abiotic conditions are quite uniform
▪ Haven’t had major change of abiotic system
o Not strong disturbance
▪ Small-scale/intensity
o Intact species pool ▪ When remove stress, species fairly easy come back with minimal intervention
• Don’t have to do much to community
• Degraded site, remove stressor, site comes back to original
[2] Hysteresis model
• Had change from original state to degraded
• When trying to recover system have to remove a lot more stress before you get a response and return
to the original state
• = Even when we removed stress, system doesn’t go back
• Have to remove more stress just to get back
• Alternative Stable States
o Ball = ecosystem
o In original state is stable
▪ Can have some disturbance
▪ But if put enough stress/disturbance and bring it past certain point, then ball rolls to
alternative stable state
▪ Will be stable on its own
• = degraded state
▪ To come back to other community, have to remove a lot of stress to push ball back
uphill so that it falls into basin attraction
• Have to go much further in terms of management
Ecosystems with Alternative Stable States may need aggressive management
• Grasses that grow fairly slowly and eventually stabilize dune
• Dune can withstand quite a bit of wind power
• Usually dunes are on shores
• But because sand is held down by roots of plants, dunes don’t move too much (i.e. sand doesn’t just
all blow away)
• Dune community can withstand quite a bit of wind
• BUT if disturb it and kill vegetation (i.e. walk on the dune all the time) might turn into really
degraded area that has almost no vegetation
• To bring it back to vegetated community, need to stabilize sand
• If some plants started trying to grow would get buried by sand storm if nothing holding sand
• Any plant that germinates will just get buried
• Need to keep down sand to allow regrowth around sand dune
• Need to stabilize sand dunes but is a lot of work so that wind doesn’t move all the sand around and
keep disturbance at bay until all the vegetation is back
o Once you destroy community hard to come back
Ecosystems with Alternative Stable States
• Shallow waters
o = quite a bit of light so plants growth throughout water column high
o = weeded lake
• Eutrophication is one of the factors that might actually prevent this
o If in area that has an area, plants usually die in winter and regrow in the spring
o Plants have to make it to surface to start growing
o Algae grows faster, so if have nutrients in water then algae can shade out vascular plants
(before plants can make it to the surface) o Vascular plants had roots in sediments that stabilized sediments
o In shallow lake will have resuspension of sediments
▪ Block the light
o System where never enough light for plants at bottom to grow to surface
o Flipped system from one dominated by vegetation to one where have no vegetation because
nothing holding things in place
• Turbidity:
o Increased turbidity = loss vegetation, then suddenly a lot of turbidity
o Need to reduce turbidity and eutrophication down past point where it shifted so that
vegetation can re-establish
• Alternative states
o Almost don’t see major shift coming
o Difficult in terms of management
o Turbidity + eutrophication increasing
o But then get catastrophic shift to another state
o Hard to bring it back
• Path for degradation isn’t same as path for restoration = hysteresis
Is Target Achieved?
• If expect system to come back to original state:
o Could set target there
• As monitor through time, can see if system is going back towards target and whether it’s going to
achieve the target
• EX: Ore mine
o Soil polluted
o Couldn’t get original forest back but got some other tree to grow back
o All of their sites came back
• EX: Calcareous soils
o Movement towards target but variability in how well different parts of system are restored
o Have diverse communities in areas
o As they’ve been restored from agriculture to grassland, different areas behave differently
o If agriculture going on for long time, might be hard to go back
Indications of divergence (i.e. not all the sites are restored)
• Abiotic conditions weren’t fully restored
• Dispersal limitation
o Are there pools of potential colonizers?
• Biological processes variable
o Which other plants are there?
o Competition, herbivory
• Important to have a target, but might not expect it to fit really well
Humpty Dumpty Model
• When falls off wall, can’t put it back together
• Original state to degraded
• Can be some recovery, but can’t get original
o Something novel
• Usually when something major happens
• Maybe don’t have same conditions before you fall off wall Is Target Achieved?
• Set target but your end community never reaches it
o Maybe because you wanted to get back to original and is not possible
o Or if have alternative target that turns out to be unrealistic
• Prairie potholes
o When tried to restore vegetation
o Agriculture all around
▪ Species pool has changed
▪ Environment has changed
What we see may not tell the whole story
• Through many forest, often put roads
• Those roads get trampled quite severely = soil compaction along roads
• When you abandon roads, things start re-growing
• When cut road, go from grasses and forbs (short vegetation to trees
o Degraded state
o But can let nature reinvade (what we do with small disturbances)
o Probably takes longer
• Or can recontour side of mountain or whatever land to try to loosen soil to enhance restoration
• But also need to look below ground
o Compaction has changed soil characteristics:
▪ Higher bulk density
▪ Lower conductivity
▪ Lower OM
▪ Lower nitrogen
• Processes in soil have not been restored compared to aboveground vegetation
• So what we see is not necessarily the whole story in terms of ecosystem functioning
Complication: Invasive Species
• Need to monitor invasive species because change story (extra stressor on degraded community)
• New Zealand:
o Lot of invasive species
o NZ split from Australia before mammals evolved so never had mammals
o Is very far from closest other land mass
o But have received quite a few species from people coming in at different times
o Have +2000 naturalized plant species
• = managing novel ecosystem
• Interactions among invasive species can lead to surprises
o A lot of connections
• Invasive species = long-term
o Easier in islands because isolated but on mainland hard to stop their spread
Past species loss may have weakened communities
• Tall canopy plants that have huge seeds
• Seeds mostly bird dispersed
• Loss of bird species = poor dispersal
o Moa
▪ 10 ft tall, 500 lbs
▪ Exterminated within 100 years of Maori inhabiting the island
• Community changes with species presence/absence Long-term effects of invasive species
• Red deer are invasive
o Graze heavily on vegetation which is already stressed by lower dispersal
o Selectively browse on saplings
o Changes forest composition
• Other plants
o Invaded and affect native plant community
o Gorse:
▪ Often introduced and is a nitrogen fixer
▪ Once if gets in, provides good services (stabilizes ground and provide nursery for
plants to grow)
▪ But inputs N into soil that didn’t have as much N
▪ Native plants that grew there before that didn’t need so much N get pushed out
Management of Whitaker’s skink
• Complications for native species management
• Have this skink only found in NZ
• Mostly places where you can find this skink is islands off shore
• Most populations are on small islands
• But only main ground population is Pukerua Bay in NZ
• Trying to manage to save skink
Complex Interactions Lead to Surprises
• Several ways of managing remaining popu